Ventilating damper



Patented sept. 12, 1933 rares PATNr Fries The Powers Regulator Company,

Chicagc,

Application January 9, 1931. Serial No. 507,626

Ny invention relates to an improvement in damper construction, particularly adapted to pivoted dampers of the type usually employed for controlling the admission of relatively large vola unies of air.

The closures or dampers for this type of air passage are usually of the louvre type ;-that is, they are composed of a plurality of relatively long and narrow plates, mounted on a longitudi-l ,10 nal pivot, the pivot being between the edges, theL edges of adjacent plates overlapping when the dampers are in closed position. These closure elements are commonly actuated by a gradually acting thermostat, the thermal condition of the .15 'ventilated space sometimes requiring a very limited admission of air', and consequently a very small damper opening.

I have found in the practical application of this type of damper that under certain condi- A tions this desired setting of the dampers cannot be eiected. For example, where the air intake is on the exterior of a building and a strong wind acts against the plates, the dampers will, as they approach the closed position, be slammed ,25 shut, although according to the temperature of the regulated space, the dampers should be partly open. This likewise occurs in other situations where a volume of air is delivered at high speed through a damper-controlled passage.

This abrupt closing action was apparently inconsistent, as the dampers were balanced-that is, they were of equal areas on the two sides of their pivots and both sides similarly exposed to the current of air. However, a study of the 5 problem-and the application of a well known principle of physics provided a solution. It may be explained as follows: As the damper swings towards closed position, a progressively increasing fraction greater than one-half of the entire volume of air is admitted around the inside-oscillating edge; in other words, all the air that comes in contact with the damper blade must pass the damper on one side. Thus a progressively increasing volume of air is attempting to pass through an opening of progressively lessening size. Consequently, as the passage space becomes restricted, the velocity of the air current increases, and the static pressure effective on the face of the damper within the restricted area is reduced. There is no corresponding pressure reduction on the outside-oscillating part and, as a result, the static pressures become unbalanced, with a preponderance on the outside part and the damper slams shut.

This effect is accentuated when, as a matter of 6 Claims. (CH. 298-3?) practical desirability, the margins of the blades overlap a seat ange or the edges of adjacent blades. As the blades near the closed position the margins that underlie the anges are shield ed from the force of impingement of the air and the unbalanced eiect is increased.

The practical application of the solved problem, contemplates an increase in area of the inside-oscillating part of the damper in a ratio corresponding to the mean of the difference of pressures effective on the two sides of the damper in the various positions from fully open to fully closed. However, to avoid an unbalanced closed condition vthat would interfere with the opening movement, I have found it desirable to so proportion the various parts that the required increase in area shall correspond substantially to the extent of overlapping of the marginal edges.

The more specic details of the invention will be more readily understood by reference to the accompanying drawing, in which:

Fig. 1 is a sectional view, somewhat diagrammatic in character, showing cold and warm air entrance passages, each controlled by a motor, actuated by a single thermostat; and 80 Fig. 2 is an enlarged detail section of a single damper.

In the drawing I have illustrated air intake passages A and B, the former conducting temperedl air and the latter cold air to the space, the temperature of which is to be regulated. 'Ihe pas sage B is shown in an outer wall C.

In each of the passages is provided seats 10, 11 and mounted in the openings are duplicate louvre type dampers. The damper blades or plates l2 are pivoted at 13, the respective damper elements being joined by links 14 for operation in unison. Operation is effected by means of the link 15 connected to the arm 16 actuated by a fluid pressure motor 17. A spring 18 resists the operation of the motor and tends to return the dampers to closed position. A thermostat 19 located in the space, the thermal condition of which is to be regulated controls both motors 17.

The mechanism described is identical for both sets of dampers and the operation is the same except that the dampers are set in opposite relation; that is, their opening and closing movements are reversed, one damper moving toward open position, while the other moves toward closed position. The pressure acting on the respective motors is controlled by a single thermostat indicated at 19 which is connected by suitable pipes to the motors.

In Fig. 2 I have shown a damper in detail in u@ the position where the unbalanced condition begins to be appreciable. The seat anges 11 denne the space within which the damper 12 oscillates. The dimensions shown in the drawing are illustrative merely of one particular size, although in a general way the same ratio should be followed for every size. From these dimensions it will be noted that the upper hal! of the damper is six and one-half inches from center to edge, while the lower half is six inches; further, that the underlap of the upper edge on the seat is approximately one-half inch.

It will be noted as indicated by the arrows, that all the volume of air between the dotted lines 20-21 being substantially seven-eights of the entire volume, is deilected toward the restricted passage around the edge of the inside-oscillating part of the blade. Thus the velocity is increased as the area o1' the passage is reduced and the static pressure is reduced in inverse ratio to the increase in velocity. By increasing the area of this side of the blade, I am able to compensate for this reduction in pressure and produce a balanced condition.

In multiple damper construction, such as shown in Fig. 1, the same condition is present. The inlet space between the outside-oscillating part of one damper and the inside-oscillating part of an adjacent damper corresponds to the restricted entrance area just described, in which area the pressure is reduced. Thus there is a reduced pressure acting on the inside of the outside-oscillating part and a normal pressure on the outside.

. This contributes to the unbalancing effect already described.

The principles herein disclosed are applicable to dampers of this character, either of single or multiple design. The exact degree 'of unbalancing of the respective damper blades, will in some instances best be determined by experiment. As a general rule however, the various parts should be so designed that the desired balanced condition will follow the use of a construction in which the increase in width of the wide side of the blade corresponds substantially to the extent of overlapping of the blade when in closed position.

It is obvious from the preceding description that the principle of operation is the same whether or no'. the margins of the damper overlap the seat or, in multiple dampers, the edges of adjacent clampers. For practical reasons, however, I prefer to utilize the type of construction shown in the drawing.

I claim:

1. The combination with an air intake opening, of a damper pivoted in said opening, a iluid pressure motor for actuating said damper, means for varying the pressure effective onsaid motor whereby to vary the position of the damper by a gradual action, the pivotal axis of the damper being between its side edges, the portion of the damper on one side of its pivot being adapted to swing inwardly toward open position, while the other part of the damper swings outwardly, the

' area of the said inside swinging part being substantially greater than the area of the outside swinging part.

2. The combination with an air intake opening, of a damper pivoted in said opening, a fluid pressure motor for actuating said damper, means for varying the pressure effective on said motor whereby to vary the position of the damper by a gradual action, the pivotal axis of the damper being between its side edges, the portion o! the damper on one side of its pivot being adapted to swing inwardly toward open position, while the other part of the damper swings outwardly, the area of the said inside swinging part being substantially greater than the area of the outside swinging part, to an extent sunicient to compensate for the diierence in pressures eiective on the outside faces of the respective inside and outside parts of the damper.

3. In combination, means providing an opening, a ilange projecting into the opening, a damper pivoted to oscillate in said opening, fluid pressure means for closing said damper with a gradual action, the portion of the damper on one side of its pivot having its margin overlapping and lying against said ilange when the damper is in closed position, said portion having an area of exposure to a vbody oi' fluid entering said opening substantially greater than the area of the portion on the opposite side of the pivot.

4. In combination, means providing an air intake opening having a seat, a damper mounted in said opening. gradually-acting uid pressure means for actuating said-damper, said damper having an oscillation pivot between its side edges, whereby the part of the damper on one side of the pivot may oscillate on the inner side of the plane of the seat, and the other part ot the damper on the outer side, the side edge of the ysaid inside-oscillating part of the damper overlapping the seat when the damper is in closed position, the parts being so proportioned that the superficial area of the said inside-oscillating part is greater than that of the outsideoscillating part to substantially the extent of the area of the seat-overlapping edge, whereby, when the damper is closed, the area of exposure to pressure of air on the inside and outside parts is substantially equal.

5. The combination with an air intake opening of a louvre damper in said opening, said damper comprising a plurality of blades, a uid pressure motor for actuating said blades in unison by a gradual action, a thermostat for actuating said motor, the pivotal axis of the blades being between their side edges, the portion of the blades on one side of their pivot being adapted to swing inwardly toward open position, while the other part of 'the blade swings outwardly the areal oi' the inside swinging part being substantially greater than the area of the outside swinging part.

6. In combination, means providing an opening, two flanges projecting into the opening, a

damper pivoted to oscillate in said opening, a

fluid pressure means for closing said damper with a gradual action, the portions of the damper on both sides of its pivot having their margins overlapping and lying against said anges when the damper is in closed position, one portion having an area of exposure to a body of iiuid entering said opening substantially greater than the area ofthe portion on the opposite side of the pivot.

MORTON O. SNEDIKER. 

